Lighting panel

ABSTRACT

A lighting panel for use in overhead lighting fixtures and the like which may readily be fabricated in plastic sheet by extrusion-embossing techniques and which minimizes veiling reflections. The panel contains a continuous pattern of triangular projections, each having three mutually substantially perpendicular surfaces projecting upward for disposition toward the light source. The base lines of the mutually perpendicular surfaces are co-planar and the pattern of projections is such that the base lines of all projections on a panel form continuous straight lines directed in three specific directions. This allows the fabrication of a relatively inexpensive engraved roller for embossing the pattern on a plastic sheet and results in a light panel which minimizes veiling reflections from the illuminated matter. The panel in accordance with the present invention provides a radial distribution of light with high lighting efficiency and with the maximum light in the area which is 30* to 60* from the vertical.

United States Patent [1 1 Jones Aug. 13, 1974 LIGHTING PANEL [75]lnventor: Bill F. Jones, Los Angeles, Calif.

[73] Assignee: J. W. Carroll & Sons, a Division of US. Industries-Ina,New York, NY.

[22] Filed: Nov. 24, 1972 [21] Appl. No.: 309,098

Primary Examiner-Joseph F. Peters Attorney, Agent, or Firm--Spensley,l-lorn & Lubitz 5 7 ABSTRACT A lighting panel for use in overheadlighting fixtures and the like which may readily be fabricated inplastic sheet by extrusion-embossing techniques and which minimizesveiling reflections. The panel contains a continuous pattern oftriangular projections, each having three mutually substantiallyperpendicular surfaces projecting upward for disposition toward thelight source. The base lines of the mutually perpendicular surfaces areco-planar and the pattern of projections is such that the base lines ofall projections on a panel form continuous straight lines directed inthree specific directions. This allows the fabrication of a relativelyinexpensive engraved roller for embossing the pattern on a plastic sheetand results in a light panel which minimizes veiling reflections fromthe illuminated matter. The panel in accordance with the presentinvention provides a radial distribution of light with high lightingefficiency and with the maximum light in the area which is 30 to 60 fromthe vertical.

13 Claims, 7 Drawing Figures LIGHTING PANEL BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to the fieldof lighting panels.

2. Disclosure Document Program This application for patent is based on adisclosure filed on July l, 1971, as Disclosure Document No. 005 990,under the Disclosure Document Program.

3. Prior Art It is commonly recognized that an artificial lightingsystem should provide not only light of the proper intensity but alsolight of the proper characteristics to minimize glare and to maximizecontrast, particularly in written or printed matter. Thus, modernlighting systems are generally comprised of a plurality of lightingfixtures, usually fluorescent, distributed over the ceiling of a roomand having lighting panels (generally plastic panels) over thefluorescent fixtures to redirect the light in an attempt to achieve thedesired result.

If printed matter is illuminated with light originating from a lightsource above and slightly forward of the reader, a considerable amountof the light may be directly reflected from the surface of the printedmatter into the eyes of the viewer. In such a case, the light will tendto be reflected both by the dark printing itself and by the backgroundso that the printing no longer appears black or dark, but insteadapproaches the lighter color of the background. Thus, the normalcontrast in the printed matter is lost, and in the extreme the printedmatter may be totally unreadable. In any event, these veilingreflections tend to reduce the contrast and make reading more difficultand uncomfortable. Of course, the effect is worse on glossy surfaces andwith particularly intense lights, but control of the light intensity andselection of the surface characteristic for the printed matter will nottotally eliminate the effect.

If printed matter is illuminated from the side, or from an areaconsiderably forward of the reader, the direct reflections from thesurface of the printed matter will not be directed upward for the eyesof the reader, but instead will be reflected at a lower angle and,therefore,

will not affect the appearance of the matter being viewed. However, someof this light which is incident upon the surface of the printed matterwill be redirected upward in a diffuse pattern in accordance with thecolor of the surface. Consequently, a white sheet of paper will clearlyappear white, whereas the black print thereon will appear in its truecolor. Thus, there are no veiling reflections and a very high degree ofcontract is obtained. Consequently, lighting from the side, rear and/orconsiderably in front of a reader is highly desirable, whereas lightingfrom a point slightly forward of the reader is undesirable. Of course,the particular position for lighting which is most undesirable forillumination of a task depends upon the orientation or angu lar positionof the task, but, in general, may be usually characterized as above andslightly forward of the reader. For minimal veiling reflections, it ishighly desirable to have the light projected as a conical annulus inwhich the light is directed at 30 to 60 from the vertical in all radialdirections.

Some patterns of prismatic lenses are known to the prior art which areintended to reduce veiling reflections. These patterns generally are ofeither of two types. The first type of pattern is a longitudinalpattern,

that is, a pattern of longitudinal raised areas generally of uniformcross-section and repetitive cross the width of the panel. Such patternscan be produced on lighting panels by extrusion techniques. By properlychoosing the geometry of the raised areas, redirection of the light isobtained. Since lighting panels are generally fabricated ofthermo-plastic materials, such as, by way of example, acrylic, rolls forembossing such a pattern in a sheet of plastic may easily be fabricated,and inexpensive lighting panels produced therefrom. Some attempts havebeen made to reduce veiling reflections in such extruded panels, as forexample, by combining the panels with a louver system or by paintingopaque areas in the extruded panel to block the path of vertical light.However, the opaque areas reduce the amount of light passingtherethrough and the panel thereby reducing the light efficiency of thepanel and such panels deflect light only to either side and not in thefore and aft direction.

The second type of pattern which has been utilized in the prior art asan attempt to reduce veiling reflections is a two-dimensional pattern,that is, a pattern of depressions which varies both across the width ofthe panel and along the length of the panel. Such a panel has a complexprismatic pattern which in the present state of the art can bemanufactured only by injection molding.

Such injection molded panels, besides their high expense, have otherdisadvantages in that they are in general useful as wrap around panelson surface mounted fixtures rather than recessed flush fixtures.

In the prior art, the type of panels heretofore known to the art toreduce veiling reflections transmit light primarily in two directionsonly, i.e., to each side of the longitudinal axis of the panel. That is,there are light panels known to the prior art which project the lightsideways in a twin beam pattern, rather than downward in order tominimize veiling reflections. This is sometimes referred to as a linearbatwing light distribution. Such panels, however, result in poor end-ondistribution and control, i.e., the light is distributed only to thesides of the panel. Prior to the present invention, no panel, andparticularly one capable of being extruded, could accomplish what couldbe termed a radial batwing distribution in which the light istransmitted in a conical configuration while eliminating the verticaldistribution, as described more fully hereinafter.

BRIEF SUMMARY OF THE INVENTION A lighting panel for use in overheadlighting fixtures and the like which may readily be fabricated inplastic sheet by embossing techniques and which minimizes veilingreflections. In the preferred embodiment the panel contains a continuouspattern of triangular projections, each having three mutuallysubstantially perpendicular surfaces projecting upward for dispositiontoward the light source. The base lines of the mutually substantiallyperpendicular surfaces are co-planar and the pattern of the projectionsis such that the base lines of all projections on the panel formcontinuous straight lines directed in three specific directions. Thisallows the fabrication of a relatively inexpensive engraved roll forembossing the pattern on a plastic sheet and results in a panel whichminimizes veiling reflections from the illuminated matter.

The embossed pattern of the present invention can be used singly orcombined with embossed or nonembossed clear and opalescent panels tofurther decrease lamp images and reduce high-angle brightness. The lensof the present invention can be embossed on clear material or thematerial can be tinted to increase the visual comfort probability.

Additionally, the panel of the present invention transmits light notonly to the sides of the panel but also in the fore and aft directionwith respect to the longitudinal axis. The light distribution to thesides of the vertical axis is sometimes referred to as batwingdistribution. By means of the present invention, a radial batwing lightdistribution is accomplished in that light distribution is in a conicalshape extending from approximately 30 from the vertical to 60 from thevertical in all directions.

The use of the wholly prismatic design of the present inventioneliminates the use of opaqued areas or other light blocking means. Thisresults in higher efficiency of light utilization, thus reducing theamount of electrical power needed to achieve the visual performanceconditions desired.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of asection of a typical ceiling having a plurality of fluorescent lightingfixtures therein.

FIG. 2 is a cross-section taken along lines 2-2 of FIG. 1 illustratingthe construction of the fluorscent fixtures.

FIG. 3 is a top view of the lighting panel of the present inventionshowing the pattern on the surface thereof.

FIG. 4 is a cross-section taken along lines 44 of FIG. 3.

FIG. 5 is a perspective view of a section of the lighting panel of thepresent invention illustrating the pattern of projections on the surfacethereof.

FIG. 6 is a polar plot of the light intensity versus direction for thelight emitted from the lighting panel of the present invention mountedin a fluorescent fixture, such as shown in FIG. 2.

FIG. 7 is a schematic representation of the lighting obtained from aplurality of fluorescent fixtures using the lighting panel of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION First referring to FIG. 1, aperspective view of two fluorescent lighting fixtures as such fixturesare characteristically mounted in a ceiling may be seen. Such lightingfixtures are characteristically arranged in a pattern throughout theceiling area so as to illuminate the entire room in as uniform manner aspossible. As viewed from within the room, the lighting fixtures comprisea front molding or frame and a lighting panel 22 to which the presentinvention is directed. I

Now referring to FIG. 2, a cross-section of one of the lighting fixturesof FIG. 1 taken along lines 22 of that figure may be seen. The lightingfixture is comprised of a frame 24, one or more fluorescent tubes 26supported by suitable mounting brackets 28, an outer molding 20 and alighting panel 30 supported by the molding 20 below the fluorescenttubes. The function of the'lighting panel 30 in modern day lightingsystems is to redistribute the illumination from the fluorescent tubesso as to reduce the vertical and nearly vertical components of lightfrom the fluorescent tubes and to redirect part of this light toward theside, thus increasing the side illumination and decreasing thesubstantially vertical illumination passing downward from the lightingpanel. The lighting panel 30 is generally a sheet of plastic with apattern embossed on the sheet so as to create a pattern of prismaticlenses to redirect the light incident thereto from the fluorescent tubesin the desired manner. It is this form of lighting panel to which thepresent invention is directed and, in particular, the present inventionis a lighting panel which may be quickly and easily fabricated from suchmaterials as thermoplastic materials by conventional extrusion embossingprocess, utilizing rollers which may be relatively easily andinexpensively fabricated.

Now referring to FIGS. 3, 4 and 5, the pattern on the upper surface ofthe lighting panel of the present invention, that is, the surface facingthe light source, may be seen. FIG. 3 is a view taken along lines 3-3 ofFIG. 2, looking downward onto the lighting panel 30. FIG. 4 is across-sectional view of the lighting panel taken along lines 4-4 of FIG.3. FIG. 5 is a perspective view of the lighting panel illustrating theform of the top surface thereof. The pattern may be most easilydescribed by identifying the characteristic lines, surfaces and pointsidentifying the pattern.

Referring first specifically to FIG. 3, and the orientation of thepattern is depicted therein, the various surfaces of the pattern mate soas to define a repetitive series of lines, all of which are co-planar.The first series of lines are lines AA having a parallel horizontaldisposition. A second set of lines identified as the BB lines, co-planarwith and having the same spacing as the first set of lines, cross thefirst set of lines at an angle of A third set of lines identified as theC-C lines are co-planar with and have the same spacing as the AA linesand the BB lines. Furthermore, the C-C lines cross the AA lines at thesame point as the BB lines and are located 60 from both the AA lines andthe BB lines. These various lines are defined by the junction oftriangular shaped flat surfaces projecting upward and mating in threesto define a plurality of apexes identified by the letter D, with each ofthe flat surfaces mating to define an apex being substantiallyperpendicular to the two adjacent surfaces cooperating to define theapex. Thus, the three sides mating to define an apex D define aprojecting surface having essentially the geometrical characteristics ofa corner of a cube.

FIG. 4 is a cross-section of the panel looking along the BB lines, theends of the lines being identified by the letter B in that figure. FIG.5 is a perspective view of a portion of the lighting panel of thepresent invention having identified thereon various of the points, linesand surfaces herein identified with respect to FIGS. 3 and 4. It will benoted that the apexes between any two BB lines lie to two rows ratherthan a single row. Thus, the apexes identified as D1 lie to the right ofthe apexes identified as D2. The lines G joining the apexes and thelines BB, as shown in FIG. 4, are the side views of the triangularsurfaces having their bases on the lines BB, whereas the lines F in FIG.4 are the lines extending from the lines BB to the apexes and definingthe junction of the other two surfaces of each protrusion.

It should be noted that though the cross-section shown in FIG. 4 wastaken about a line perpendicular to the BB lines, the cross-section ofthe pattern taken along AA lines and C-C lines is also the same. Thus,

the pattern hereinabove described may be formed in a sheet of plastic byforming parallel, equally spaced V grooves of the proper angle in afirst direction, in a second direction 60 to one side of the firstdirection, and in a third direction 60 to the opposite side of the firstdirection, in a pattern such that the junction of the two sides of thesecond and third set of V grooves cross the junction of the two sides ofthe first set of V grooves at the same points.

In order for the three surfaces projecting upward to an apex to besubstantially perpendicular to each other, that is, to have thegeometric properties of a corner of a box, each side of the V groovesshould be disposed at an angle of from 50 to 60 upward from the plane ofthe sheet of plastic thus causing the V grooves to have an includedangle of from 80 to 60. As a result of the V grooves, the linesidentified by the letter F in FIG. 4 will define the complimentary angleof from 40 to 30 upward from the plane of the sheet of plastic. In thepresently preferred embodiment, each side of the V grooves is disposedat an angle of 57 upward from the plane of the sheet, thus resulting inan included angle of 66 such that the lines F in FIG. 4 are at an angleof 33 upward from the plane of the sheet of plastic. Thus, each surfaceE of the pattern is inclined at an angle of 33 with respect to thevertical.

The function of the pattern on the lighting panel of the presentinvention may be described as follows: Light directed from immediatelyabove onto the lighting panel will strike one of the surfaces of theprotrusion at an angle of 33, since all surfaces in the pattern areinclined with respect to the vertical by this angle. Since the light isentering a medium of higher index of refraction, the light path will becurved toward a perpendicular to the surface and, thus, deflectedsomewhat to the side in comparison to its initial vertical path. Thelower surface of the panel being flat as shown in FIGS. 4 and 5, thelight will strike the lowersurface at a substantial angle and, uponpassing therethrough into a medium (air) having a lower index ofrefraction,

will be further deflected away from the vertical. By

way of example, if the lighting panel is fabricated from a polystyrenesheet having an index of refraction of approximately 1.6, most of thelight incident upon the surfaces as hereinabove described will betransmitted therethrough, rather than reflected, and the light emergingfrom the lower surface of the panel will have a total deflection fromthe vertical of approximately 57. The direction of any particular lightray will -depend upon which of the triangular surfaces it initiallyentered in the pattern on the upper surface of the panel and, ingeneral, light rays which initially were purely vertical with respect tothe panel will be deflected to the side of six directions approximately60 apart.

From the lower (non-embossed) side of the panel, the elements act toredirect any light coming into the panel from directly below back in itsoriginal direction. By the reciprocity of light rays, this means that nolight from above the panel can penetrate into the angles directly belowthe panel. (This redirection is generally illustrated by the light ray29 in FIG. 2. Total theoretical reflection for redirection willgenerally be achieved when somewhat different surface angles are used,depending upon the index of refraction of material).

Referring now to FIG. 2, it will be seen that only a very limitedportion of the lighting panel 30 is located immediately below any of thefluorescent tubes 26, and

further, the portion of the panel located immediately below any of thetubes will receive substantial illumination from the tubes other thanfrom the portion of the tube directly above, that is, from portions ofthe tube longitudinally displaced from that section of the panel andfrom the reflective surface of the fixture. Consequently, a considerableamount of light will strike the top surface of the panel at substantialangles from the vertical and, therefore, the light projecting downwardfrom the bottom surface of the panel will be distributed over allangles. In fact, some of the light striking the upper surface of thepanel at certain angles will be deflected on passing through the panel,so as to be emitted from the panel in a vertical downward direction.However, the amount of light emitted from the panel in a verticaldirection is limited and, in general, the intensity of the light emittedto the side and fore and aft of the panel will be substantially higherthan the vertical component. By way of example, the distribution ofintensity versus angle in a typical installation using the panel of thepresent invention is as shown in FIG. 6. This figure is a plot, in apolar coordinate system, of the intensity of illumination versusdirection, with the intensity being indicated by the distance from point50 to a point on the curve, and the direction being indicated by thedirection of a line point 50 to the corresponding point on the curve. Itwill be noted while there is substantial vertical illumination, theillumination to each side in any azimuthal plane is substantiallygreater than the vertical illumination. Furthermore, the saidillumination is distributed over a substantial angle so that strongveiling reflections will, in general, not be obtained regardless of theorientation of the task. Thus, the objects of eliminating particularlyintense vertical or near vertical illumination and of furthereliminating particularly intense illumination in any specific direction,have been achieved with the panel of the present invention. (Orientingthe panel so that the pattern is on the surface directed away from thelight source will also reduce the vertical component of illuminationsince the projections will act as retrodirective reflectors as thevertical and near vertical components of light. However, thisillumination will be lost unless the top surface of the panel and/or thefixture enclosure are adapted to reflect this light downward again at adifferent angle.)

Now referring to FIG. 7, a schematic representation of a student in aclassroom illuminated by a plurality of overhead fixtures utilizing thelighting panel of the present invention may be seen. The lightingdistribution of FIG. 6 is approximately indicated by the length of thelines representing the light rays in FIG. 7. It will be noted that thetable 52 in front of the student 54 is more strongly illuminated bylight fixtures 56 and to each side of the student than by the fixture 58immediately overhead. It should also be noted that the lighting panelshave substantial areas, typically on the order of 2 feet by 4 feet, andthus even the light reaching a printed page in front of the student froma particular light panel is not light having a fixed direction, but islight distributed over a substantial angle dependent upon the size andorientation of the lighting panel with respect to the printed matter.(Typically, a significant percentage of a ceiling area is occupied bysuch areas.)

Other patterns for use on lighting panels which will generally achievethe optical objects of the present invention are also known. However,the pattern of the present invention is particularly advantageous sincelighting panels of the present invention may be readily fabricated by anextrusion-embossing process using simple and inexpensive rolls. By wayof example, the pattern shown in detail in FIGS. 3, 4 and 5 wascharacterized as being formable in a sheet of plastic by creatingparallel, equally spaced V grooves of the proper angle in a firstdirection, in a second direction 60 one side of the first direction, andin a third direction 60 to the opposite side of the first direction, ina pattern such that the junction of the two sides of the second andthird set of V grooves cross the junction of the two sides of the firstset of V grooves at the same points. The roll for producing thispattern, of course, must have the negative of the pattern of the surfacethereof.

In some instances and in the presently preferred embodiment of thepresent invention, an overlay sheet is affixed to the embossed surface,i.e., the upper surface of the panel to reduce any visible lamp image.In the presently preferred embodiment a high light transmission acrylicoverlay of typical thickness such as an 0.040 to 0.060 inch thick sheetof opal acrylic is used. This does not effect the light distributionpreviously described but serves only to reduce any visible image of thelamp within the fixture.

ln other instances, a second panel 31 may be affixed to the non-embossedsurface, i.e., the lower surface of the panel, in order to modify thedistribution or constitute a decorative element. Or, a decorative ormodifying pattern may be impressed into the lower (nonembossed) surfaceitself. One of the reasons for an embodiment utilizing such a secondpanel is to redirect light rays to reduce high-angle luminance.

The advantage of the particular pattern used on the panel of the presentinvention is that the pattern is the net result of a plurality ofgenerated surfaces and a suitable roll (press, mold and the like,depending upon the particular fabrication process desired) for embossingthe pattern on a sheet of thermoplastic may similarly be easilygenerated. Also, while the particular pattern described in detail aboveis comprised of a pattern of projections having three mutuallyperpendicular surfaces, the angles generating these surfaces may bevaried somewhat from the values given herein so that the surfacesdefining each projection are not perpendicular. By varying the angle,the distribution of illumination may be varied. Similarly, the V groovesand thus the plurality of triangular shaped surfaces defining thepattern may be curved somewhat, that is, the V grooves may have curvedlegs, perhaps near their junction to also vary the distribution ofillumination created by the panel. These and other variations of thepresent invention panel may readily be designed and constructed by oneskilled in the art from the disclosure provided herein without departingfrom the spirit and scope of the present invention.

1 claim:

1. A lighting panel having on one surface thereof a pattern ofprotrusions each defined by three generally flat triangular surfaces,each of said triangular surfaces having first and second sides and abase, and mating the other two of said three triangular surfacesdefining each of said protrusions on said first and second sidesthereof, each of said bases of said three triangular surfaces definingeach of said protrusions being substantially coincident with the base ofone of said triangular surfaces defining an adjacent protrusion, all ofsaid basesbeing substantially coplanar, each of said three triangularsurfaces being disposed at approximately to with respect to the plane ofsaid bases.

2. The lighting panel of claim ll wherein said three triangular surfacesdefining each of said protrusions being mutually substantiallyperpendicular surfaces.

3. The lighting panel of claim 2 wherein there is affixed to the surfaceopposite said one surface a second panel designed to further reduceveiling reflections.

4. The lighting panel of claim 1 wherein there is affixed to said onesurface a high transmission overlay means for damping lamp images.

5. The lighting panel of claim 1 wherein there is impressed into thesurface opposite said one surface a pattern designed to further reduceveiling reflections.

6. A lighting panel having on one surface thereof a pattern ofprotrusions defined by a first set of parallel, equidistantly spaced Vgrooves directed downward into said panel; a second set of parallel Vgrooves directed downward into said panel; said second set of V grooveshaving the same spacing as said first set and crossing said first set atan angle of approximately 60; and a third set of parallel V groovesdirected downward into said panel; said third set of V grooves havingthe same spacing as said first set and crossing said first and secondsets at an angle of approximately 60; said first, second and third setsof V grooves being disposed so that the lines defined by the junction ofthe two sides of each of said V grooves are substantially coplanar,

each of said two sides of each of said V grooves being disposed atapproximately 50 to 60 with respect to the plane of said lines definedby the junction of the two sides of each of said V grooves.

7. The lighting panel of claim 6 wherein each of said two sides of eachof said V grooves are disposed at approximately 57 with respect to theplane of said lines defined by the junction of the two sides of each ofsaid V grooves.

8. The lighting panel of claim 6 wherein there is affixed to the sideopposite said one side of the panel an acrylic sheet of high lighttransmitting diffusing material for damping lamp images visible throughsaid panel.

9. In a lighting fixture of the type including a housing and a lightsource within the housing, a lighting panel having first and secondsurfaces, and having on said first surface thereof a pattern ofprotrusions each defined by three generally triangular surfaces; each ofsaid triangular surfaces having first and second sides and a base andmating the other two of said three triangular surfaces defining each ofsaid protrusions on said first and second sides thereof; each of saidbases of said three triangular surfaces defining each of saidprotrusions being substantially coincident with the base of one of saidtriangular surfaces defining an adjacent protrusion, all of said basesbeing substantially coplanar; said triangular surfaces being inclinedwith respect to the plane of said bases by a predetermined angle so thatlight coming directly toward said second surface is redirectedback-toward its original direction by said pattern.

10. An improved lighting panel comprising a sheet having first andsecond surfaces, and having on said first first surface thereof apattern of protrusions, each of said protrusions having a plurality ofsurfaces excur, said predetermined angle being an angle larger than thelimiting angle at which said light reflected by said first of saidprotrusion surfaces would be totally reflected by said second of saidprotrusion surfaces, whereby light impinging on said panel substantiallyperpendicular to said second panel surface will be reflected by saidpattern back toward the direction said light originated as a result ofthe reflection of said light from at least a first and a second surfaceof said protrusons.

t 11. The lighting panel of claim 10 wherein each of said protrusions isdefined by a plurality of generally flat surfaces so that across-section of each of said protrusions is a polygon.

12. The lighting panel of claim 11 wherein said crosssection is anequilateral triangle.

13. A lighting panel having on one surface thereof a pattern defined bya plurality of groups of three generally triangular surfaces, each ofsaid triangular surfaces having first and second sides and a base, andmating the other two of said three triangular surfaces on said first andsecond sides thereof, each of said bases of said three triangularsurfaces in a group being substantially coincident with the base of oneof said triangular surfaces in an adjacent group, all of said basesbeing substantially coplanar, each of said three triangular surfacesbeing disposed at approximately 50 to 60 with respect to the plane ofsaid bases.

1. A lighting panel having on one surface thereof a pattern ofprotrusions each defined by three generally flat triangular surfaces,each of said triangular surfaces having first and second sides and abase, and mating the other two of said three triangular surfacesdefining each of said protrusions on said first and second sidesthereof, each of said bases of said three triangular surfaces definingeach of said protrusions being substantially coincident with the base ofone of said triangular surfaces defining an adjacent protrusion, all ofsaid bases being substantially coplanar, each of said three triangularsurfaces being disposed at approximately 50* to 60* with respect to theplane of said bases.
 2. The lighting panel of claim 1 wherein said threetriangular surfaces defining each of said protrusions being mutuallysubstantially perpendicular surfaces.
 3. The lighting panel of claim 2wherein there is affixed to the surface opposite said one surface asecond panel designed to further reduce veiling reflections.
 4. Thelighting panel of claim 1 wherein there is affixed to said one surface ahigh transmission overlay means for damping lamp images.
 5. The lightingpanel of claim 1 wherein there is impressed into the surface oppositesaid one surface a pattern designed to further reduce veilingreflections.
 6. A lighting panel having on one surface thereof a patternof protrusions defined by a first set of parallel, equidistantly spacedV grooves directed downward into said panel; a second set of parallel Vgrooves directed downward into said panel; said second set of V grooveshaving the same spacing as said first set and crossing said first set atan angle of approximately 60*; and a third set of parallel V groovesdirected downward into said panel; saId third set of V grooves havingthe same spacing as said first set and crossing said first and secondsets at an angle of approximately 60*; said first, second and third setsof V grooves being disposed so that the lines defined by the junction ofthe two sides of each of said V grooves are substantially coplanar, eachof said two sides of each of said V grooves being disposed atapproximately 50* to 60* with respect to the plane of said lines definedby the junction of the two sides of each of said V grooves.
 7. Thelighting panel of claim 6 wherein each of said two sides of each of saidV grooves are disposed at approximately 57* with respect to the plane ofsaid lines defined by the junction of the two sides of each of said Vgrooves.
 8. The lighting panel of claim 6 wherein there is affixed tothe side opposite said one side of the panel an acrylic sheet of highlight transmitting diffusing material for damping lamp images visiblethrough said panel.
 9. In a lighting fixture of the type including ahousing and a light source within the housing, a lighting panel havingfirst and second surfaces, and having on said first surface thereof apattern of protrusions each defined by three generally triangularsurfaces; each of said triangular surfaces having first and second sidesand a base and mating the other two of said three triangular surfacesdefining each of said protrusions on said first and second sidesthereof; each of said bases of said three triangular surfaces definingeach of said protrusions being substantially coincident with the base ofone of said triangular surfaces defining an adjacent protrusion, all ofsaid bases being substantially co-planar; said triangular surfaces beinginclined with respect to the plane of said bases by a predeterminedangle so that light coming directly toward said second surface isredirected back toward its original direction by said pattern.
 10. Animproved lighting panel comprising a sheet having first and secondsurfaces, and having on said first first surface thereof a pattern ofprotrusions, each of said protrusions having a plurality of surfacesextending toward an apex, each of said protrusion surfaces beinginclined at a predetermined angle with respect to a first lineperpendicular to said second panel surface, said predetermined anglebeing an angle smaller than the limiting angle at which total reflectionof light impinging on a first of said protrusion surfaces from withinsaid panel and directed along said first line would occur, whereby totalreflection of said light toward a second of said protrusion surfaceswould occur, said predetermined angle being an angle larger than thelimiting angle at which said light reflected by said first of saidprotrusion surfaces would be totally reflected by said second of saidprotrusion surfaces, whereby light impinging on said panel substantiallyperpendicular to said second panel surface will be reflected by saidpattern back toward the direction said light originated as a result ofthe reflection of said light from at least a first and a second surfaceof said protrusions.
 11. The lighting panel of claim 10 wherein each ofsaid protrusions is defined by a plurality of generally flat surfaces sothat a cross-section of each of said protrusions is a polygon.
 12. Thelighting panel of claim 11 wherein said cross-section is an equilateraltriangle.
 13. A lighting panel having on one surface thereof a patterndefined by a plurality of groups of three generally triangular surfaces,each of said triangular surfaces having first and second sides and abase, and mating the other two of said three triangular surfaces on saidfirst and second sides thereof, each of said bases of said threetriangular surfaces in a group being substantially coincident with thebase of one of said triangular surfaces in an adjacent group, all ofsaid bases being substantially coplanar, each of said three triangularsuRfaces being disposed at approximately 50* to 60* with respect to theplane of said bases.